Field of the Disclosure
The present application relates to an organic light emitting display device and a method for fabricating the same.
Description of the Related Art
Organic light emitting display devices are self-luminous elements that cause an organic light emitting layer to emit light by the recombination of electrons and holes. Organic light emitting display devices have high brightness, low operating voltage, and ultra-thin design.
An active-matrix organic light emitting display device (AMOLED) includes pixels arranged in a matrix to display an image. Each pixel includes an organic light emitting diode and a cell driver that independently drives the organic light emitting diode. The cell driver includes at least two thin film transistors and a storage capacitor to control the amount of light emission from the organic light emitting diode by controlling the amount of electric current fed to the organic light emitting diode in response to a data signal.
The organic light emitting diode includes an emissive layer of organic materials disposed between an upper electrode and a lower electrode. The organic light emitting diode emits light by energy generated when an exciton, which is a hole-electron pair formed by the combination of a hole fed from the lower electrode and an electron received from the upper electrode within the emissive layer, returns to the ground state.
The organic light emitting display devices include bottom emission devices and top emission devices depending on the direction that emitted light exits the device. For bottom emission devices, light emitted passes through the bottom of the substrate, i.e., from the organic light emitting layer toward the lower electrode. For top emission devices, light emitted passes through the top of the substrate, i.e., from the organic light emitting layer toward the upper electrode.
The upper electrode of a top emission organic light emitting display device is made thin enough to pass light through the upper electrode, which causes an increase in the resistance of the upper electrode. Organic light emitting display devices, in related art, include a larger screen and a larger area of the upper electrode, an increased resistance of the upper electrode, and a large voltage drop (IR drop). As a result, the large IR drop in the organic light omitting display devices of related art can result in a rise in power consumption and non-uniformity in the brightness of the display devices, and decreased reliability.